Seed treatment fungicides for control of plant diseases

ABSTRACT

A method for combatting plant fungi in a plant, which comprises applying to the seeds or tubers of the plant, an effective amount of a fungicidal composition comprising a fungicidally effective amount of a 2-alkoxyiminoacetamide compound, optionally in admixture with one or both of an alkylene bis-dithiocarbamate complex salt and a thiophanate compound. Fungicidal compositions comprising a fungicidally effective amount of a 2-alkoxyimino-acetamide compound, an alkylene bis-dithiocarbamate complex salt, and a thiophanate compound, are also described.

This application is a divisional U.S. application Ser. No. 09/132,927, filed Aug. 12, 1998, which claims the benefit of U.S. Provisional application Ser. No. 60/059,293, filed Sep. 18, 1997, entitled "SEED TREATMENT FUNGICIDES FOR CONTROL OF PLANT DISEASES."

FIELD OF THE INVENTION

This invention relates to a method for controlling fungus diseases in plants by applying to the seed or tuber a fungicidally effective amount of a 2-alkoxyimino-acetamide compound such as cymoxanil, optionally in admixture with one or more of an alkylene bis-dithiocarbamate complex salt such as mancozeb, and a thiophanate compound such as thiophanate-methyl. This invention also relates to a fungicidal composition comprising, in a fungicidally effective aggregate amount, a 2-alkoxyiminoacetamide compound, an alkylene bis-dithiocarbamate complex salt, and a thiophanate compound.

BACKGROUND OF THE INVENTION

Late Blight is the devastating disease that affected the Irish potato crop over 150 years ago. Today, however, the Late Blight fungus, Phytophthora infestans, is much different than its ancestors. New strains of P. infestans have evolved that are fungicide resistant and which are more aggressive with respect to pathogenicity on the potato tuber. As a result, the disease can now be introduced into potato fields by means of infected seed tubers more efficiently than in the past.

It is the purpose of this invention to provide a novel method for combatting plant fungi, particularly phytopathogenic fungi such as Phytophthora infestans. It is a purpose to provide a novel fungicidal composition useful for combatting plant fungi, particularly phytophogenic fungi such as Phytophthora infestans.

SUMMARY OF THE INVENTION

This invention relates to a method for combatting plant fungi in a plant, which comprises applying to the seeds or tubers of the plant, a fungicidally effective amount of:

a) a 2-alkoxyiminoacetamide compound of the formula: ##STR1## wherein R is methyl or ethyl and R¹ hydrogen, C₁ -C₄ alkyl or allyl, preferably, C₁ -C₄ alkyl, more preferably, methyl or ethyl; or

b) the 2-alkoxyiminoacetamide compound in admixture with one or more compounds selected from the group consisting of:

i) an alkylene bis-dithiocarbamate complex salt of the formula: ##STR2## wherein R⁴ and R⁵ are each, independently, hydrogen or C₁ -C₆ alkyl, preferably, hydrogen or C₁ -C₄ alkyl, more preferably, hydrogen, methyl or ethyl; Q is Zn, Fe, or Cu, preferably, Zn; and the ratio of x to y is from about 3:1 to about 100:1, preferably, about 5:1 to about 20:1, more preferably, about 6:1 to about 10:1. and

ii) a thiophanate compound of the formula: ##STR3## wherein R² and R³ are each, independently, C₁ -C₆ alkyl, preferably, C₁ -C₄ alkyl, more preferably, methyl or ethyl.

This invention further relates to a fungicidal composition comprising:

a) a 2-alkoxyiminoacetamide compound of the formula: ##STR4## wherein R is methyl or ethyl and R¹ hydrogen, C₁ -C₄ alkyl or allyl, preferably, C₁ -C₄ alkyl, more preferably, methyl or ethyl;

b) an alkylene bis-dithiocarbamate complex salt of the formula: ##STR5## wherein R⁴ and R⁵ are each, independently, hydrogen or C₁ -C₆ alkyl, preferably, hydrogen or C₁ -C₄ alkyl, more preferably, hydrogen, methyl or ethyl; Q is Zn, Fe, or Cu, preferably, Zn; and the ratio of x to y is from about 3:1 to about 100:1, preferably, about 5:1 to about 20:1, more preferably, about 6:1 to about 10:1; and

c) a thiophanate compound of the formula: ##STR6## wherein R² and R³ are each, independently, C₁ -C₆ alkyl, preferably, C₁ -C₄ alkyl, more preferably, methyl or ethyl,

in an effective aggregate amount.

DESCRIPTION OF THE INVENTION

The 2-alkoxyiminoacetamide compounds, alkylene bis-dithiocarbamate complex salts, and thiophanate compounds useful in the method and composition of this invention, are known in the art, as are methods for their preparation. See, e.g., U.S. Pat. Nos. 3,957,847; 3,379,610; and 5,571,443, respectively.

The method and composition of this invention are particularly suitable for use against Phytophthora infestans on or in potato plants and tubers.

The composition of this invention and the compounds useful in the method of this invention can be formulated in conventional ways. Examples of useful formulations include slurries, solid seed coatings, soaks, dusts on the surface of the seed or tuber, solutions, suspensions, emulsions, wettable powders, emulsifiable concentrates, and the like. The formulations, in general, comprise about 1% to 99% by weight of active ingredient. The formulations can additionally comprise additional additives such as surfactants, solid or liquid diluents, pigments, thickeners, and the like. The method of application of the formulations to the seeds or tubers can vary depending, e.g., on the compounds and/or the formulation used.

In general, the seed or tuber should be treated with about 50 to about 1200 ppm, preferably between about 300 to about 900 ppm, most preferably, about 700 ppm, per 100 pounds ("cwt") of seed or tuber, of the composition of this invention or of the compounds useful in the method of this invention.

This invention preferably relates to a method for combatting plant fungi in a plant, which comprises applying to the seeds or tubers of the plant, an effective amount of a fungicidal composition comprising a fungicidally effective amount of:

a) cymoxanil; or

b) cymoxanil in admixture with one or more of the group consisting of mancozeb and thiophanate-methyl.

This invention further preferably relates to a fungicidal composition comprising cymoxanil, mancozeb and thiophanate-methyl, in an effective aggregate amount.

Cymoxanil, mancozeb and thiophanate-methyl are all known compounds.

Cymoxanil (a foliar fungicide sold under the trademarks CURZATE and DPX-3217) is 2-cyano-N-[(ethylamino)carbonyl]-2-(methoxyimino)-acetamide.

Mancozeb (a fungicide sold under the trademarks MANZATE-200 and DITHANE M-45) is a mixture of [[1,2-ethanediylbis-(carbamodithioato)](2-)]manganese and [[1,2-ethanediylbis(carbamothioato)](2)-]zinc.

Thiophanate-methyl (a systemic fungicide sold under the trademarks TOPSIN M and NF-44) is dimethyl[1,2-phenylene-bis-(iminocarbono-thioyl)-bis-[carbamate].

In the method of this invention wherein cymoxanil is admixed with thiophanate-methyl, in general, satisfactory results can be obtained when the weight ratio of cymoxanil:thiophanate-methyl is from about 1:3 to 3:1, preferably 1:2 to 2:1, and more preferably, 1:1.5 to 1.5:1.

In the method of this invention wherein cymoxanil is admixed with mancozeb, in general, satisfactory results can be obtained when the weight ratio of cymoxanil:mancozeb is from about 1:16 to 3:1, preferably 1:8 to 2:1, and more preferably, 1:3 to 1.5:1.

In the method of this invention wherein cymoxanil, mancozeb and thiophanate-methyl are admixed, in general, satisfactory results can be obtained when the weight ratio of cymoxanil:mancozeb:thiophanate-methyl is from about 3:1:1 to about 1:16:6, preferably, about 1.5:1:1 to about 1:8:3.

Similarly, in the composition of this invention, in general, satisfactory results can be obtained when the weight ratio of cymoxanil:mancozeb:thiophanate-methyl is from about 3:1:1 to about 1:16:6, preferably, about 1.5:1:1 to about 1:8:3.

The formulations can comprise from 0 to about 20% of an agriculturally acceptable surfactant such as wetting and dispersing agents, e.g., the condensation product of formaldehyde with naphthalene sulphonate, an alkylarylsulphonate, a lignin sulphonate, a fatty sulphate, an ethoxylated alkylphenol and an ethoxylated fatty alcohol. The formulations can additionally comprise from about 10 to about 99% of an agriculturally acceptable solid or liquid diluent, including carriers, such as talc, zeolites, Alder bark, kaolin, diatomaceous earth, mineral oil, water, and the like.

The following examples are provided to illustrate the present invention.

EXAMPLES Example 1

(A) A potato dust inert system (PDIS) was prepared by blending the following three inert diluents in a ribbon blender: talc (Cyprus BT-200) (48.39% w/w), zeolite (16.12% w/w) , and Alder bark (35.49% w/w).

The dusts listed in Table 1 below were prepared by blending PDIS and the compounds at the concentrations indicated in a ribbon blender and were evaluated for activity against P. infestans at the rate of application of active ingredient indicated.

                  TABLE 1                                                          ______________________________________                                                                             Rate of                                      Dust  Percent Percent Application                                              No. Compound (w/w) PDIS (w/w) (ppm/cwt.sup.1)                                ______________________________________                                         1     Cymoxanil   10.5     89.5     500                                          2 Cymoxanil 5.3 91.5 250                                                        Topsin.sup.2 3.2  150                                                         3 Dimethomorph.sup.3 10.5 89.5 500                                             4 Dimethomorph 5.3 91.5 250                                                     Topsin 3.2  150                                                               5 Propamocarb.sup.4 10.5 89.5 500                                              6 Propamocarb 5.3 91.5 250                                                      Topsin 3.2  150                                                               7 Topsin 5.3 94.7 250                                                          8 Topsin 2.6 89.9 250                                                           Mancozeb 7.5  600                                                           ______________________________________                                          .sup.1 parts per million per hundred lbs. of seed (tuber)                      .sup.2 thiophanatemethyl                                                       .sup.3 (E,Z) 4[3(4-chlorophenyl)-3-(3,4-dimethoxyphenyl)                       acryloyl]morpholine                                                            .sup.4 Propyl [3(dimethylamino)propyl]carbamate                          

(B) The in-vitro screening procedure was conducted as follows:

Potato tubers were removed from 5° C. storage and allowed to come to room temperature. The tubers were then washed with tap water and sterilized in 5% commercial bleach (Clorox) for 10 minutes. The tubers were then rinsed in sterile distilled water and dried.

Phytophthora infestans was grown on agar plates at 18° C. for 10-14 days. 20 ml. of 5° C. sterile distilled water were then added to each plate. The agar was then agitated or cut into smaller sections and placed at 10-12° C. for 2 hours to release zoospores.

Tubers were cut into uniform sized slices (1 cm thick). Each dust was applied to 20 slices at 0.5 lb/cwt. Two sets of 20 potato slices were left untreated with dust and used as controls. Each dusted potato slice was then placed on sterile moistened filter paper in a sterile petri dish.

A zoospore suspension was quantified to a concentration of 20,000 spores/ml. 100 μl of this spore suspension was then applied to a sterile filter paper disk. One such treated disk was placed in the center of each potato slice. One set of 20 undusted potato slices were not inoculated and used as a sterile control.

Each potato slice was then placed in the dark at 18° C. for 7 days. After the 7 days, the disease state of each potato slice was assessed.

In Table 2 below, growth and sporulation of P. infestans for each potato slice was rated on a plus (+) or minus (-) scale. A minus indicates no growth of the P. infestans whereas a plus indicates growth. Growth was measured as minimal (+), good (++), or good and sporulation (+++)

                  TABLE 2                                                          ______________________________________                                         GROWTH AND SPORULATION OF P. INFESTANS                                                  Dust No. Growth                                                       ______________________________________                                                1      -                                                                  2 -                                                                            3 -                                                                            4 -                                                                            5 +++                                                                          6 ++                                                                           7 +                                                                            8 -                                                                            Untreated +++                                                                  Sterile -                                                                    ______________________________________                                    

Example 2

(A) Dusts were prepared as described in Example 1 above.

(B) The in-vivo screening procedure was conducted as follows:

Potato tubers were removed from 5° C. storage and allowed to come to room temperature. The tubers were then washed with tap water and sterilized in 5% commercial bleach (Clorox) for 10 minutes. The tubers were then rinsed in sterile distilled water and dried.

Phytophthora infestans was grown on agar plates at 18° C. for 10-14 days. 20 ml. of 5° C. sterile distilled water were then added to each plate. The agar was then agitated or cut into smaller sections and placed at 10-12° C. for 2 hours to release zoospores. A zoospore suspension was quantified to a concentration of 20,000 spores/ml.

Small punctures were made in the tubers with a sterile needle and the punctured tubers were then dipped into the suspension of P. infestans zoospores. The tubers were then incubated at 15° C. with 95% relative humidity for 7-10 days. After the incubation the tubers were then cut into 2-4 oz. pieces. Each dust was applied to 15 pieces at 0.5 lb/cwt or according to manufacturer's directions. One set of 15 pieces was left untreated and used as a control.

Potatoes not dipped in the zoospores were also cut into 2-4 oz. pieces and one set of 15 uninoculated potato pieces was used as a sterile control.

The potato pieces were then placed in sandy soil and incubated at 17° C. days and 13° C. nights for 32 days. Growth after emergence was monitored for 14-28 days. Disease symptoms were visually rated. Stem/leaf tissue was assayed for P. infestans on appropriate media.

Finally, potato seed pieces were then removed and cut in half and disease presence was visually assessed.

The results of this test are presented below in Tables 3 and 4.

                  TABLE 3                                                          ______________________________________                                         Germination and Emergence Results                                                              Emergence (%)                                                                             Germination (%)                                       Dust No. Day 14 Day 32                                                       ______________________________________                                         1           33.3       100                                                       2 33.3 100                                                                     3 26.7 80                                                                      4 33.3 53.3                                                                    6 20 40                                                                        8 6.7 6.7                                                                      Untreated 20 13.3                                                              Sterile 33.3 100                                                             ______________________________________                                    

                  TABLE 4                                                          ______________________________________                                         TUBER AND STEM HEALTH                                                            Dust No.    A.sup.1 (%)                                                                            B.sup.2 (%)                                                                              C.sup.3 (%)                                                                          D.sup.4 (%)                              ______________________________________                                         1         0       0           26.7  73.3                                         2 0 0 0 100                                                                    3 20 26.7 53.3 0                                                               4 40 13.3 40 0                                                                 6 60 20 20 0                                                                   8 93.3 6.7 0 0                                                                 Untreated 86.7 13.3 0 0                                                        Sterile 0 0 0 100                                                            ______________________________________                                          .sup.1 Blighted tuber; No emergence                                            .sup.2 Blighted tuber; Smallsized infected stems                               .sup.3 Blighted tuber; Averagesized infected stems                             .sup.4 Clean tubers; Healthy uninfected stems                            

Example 3

The following new dusts in Table 5 were prepared as described in Example 1.

                  TABLE 5                                                          ______________________________________                                                                            Rate of                                       Dust  Percent Percent Application                                              No. Compound (w/w) PDIS (w/w) (ppm/cwt)                                      ______________________________________                                         9      Cymoxanil 5.3       94.7    250                                           10 Cymoxanil 2.1 94.7 100                                                       Topsin.sup.2 3.2  150                                                         11 Cymoxanil 4.2 92.6 200                                                       Topsin 3.2  150                                                               12 Cymoxanil 2.1 92.2 100                                                       Mancozeb 2.5  100                                                              Topsin 3.2  150                                                               13 Topsin 5.2 87.3 500                                                          Mancozeb 7.5  600                                                           ______________________________________                                    

These dusts were tested using the procedure described in Example 2 above. The results of this testing is shown in Table 6 below.

                  TABLE 6                                                          ______________________________________                                         EMERGENCE AND TUBER AND STEM HEALTH                                                    Emergence (%)      Infection (%)                                       Dust No.                                                                               Day 15   Day 23   Day 35 Tubers Stems                                  ______________________________________                                          9      0        20       80     20     0                                        10 0 0 60 40 33.3                                                              11 0 20 100 40 33.3                                                            12 20 80 100 0 0                                                               13 0 0 0 100 no                                                                     stems                                                                     Untreated 0 0 0 100 no                                                              stems                                                                     Sterile 0 100 100 0 0                                                        ______________________________________                                    

Example 4

The following dusts in Table 7 were prepared as described in Example 1.

                  TABLE 7                                                          ______________________________________                                                                             Rate of                                      Dust  Percent Percent Application                                              No. Compound (w/w) PDIS (w/w) (ppm/cwt)                                      ______________________________________                                         14    Mancozeb(80%)                                                                               10.0     90.0    400                                          15 Cymoxanil(96%) 2.1 97.9 100                                                 16 Cymoxanil(96%) 2.1 90.9 100                                                  Mancozeb(80%) 7.5  300                                                        17 Topsin(95%) 3.2 92.8 150                                                     Cymoxanil(50%) 4.0  100                                                       18 Topsin(95%) 3.2 84.7 150                                                     Mancozeb(80%) 10.0  400                                                        Cymoxanil(96%) 2.1  100                                                       19 Topsin(95%) 3.2 87.3 150                                                     Mancozeb(80%) 7.5  300                                                         Cymoxanil(96%) 2.1  100                                                     ______________________________________                                    

These dusts (as well as Dust Nos. 7 and 8) were tested using the procedure described in Example 2 above using Russet Burbank tubers. The results of this testing (10 replications/treatment) are shown in Table 8 below.

                  TABLE 8                                                          ______________________________________                                         EMERGENCE AND STEM HEALTH                                                                Emergence (%)   Infection (%)                                        Dust No.  Day 14      Day 28  Stems                                            ______________________________________                                          7        0           0       no stems                                            8 10 10 100                                                                   14 0 10 100                                                                    15 30 40 25                                                                    16 20 40 0                                                                     17 10 30 33                                                                    18 30 40 0                                                                     Untreated 0 0 no stems                                                         Sterile 60 100 0                                                             ______________________________________                                    

Example 5

The dusts prepared in Example 4 above (as well as Dust Nos. 7 and 8) were tested using the procedure described in Example 2 above using Red Nordland tubers. The results of this testing (7 replications/treatment) are shown in Table 9 below.

                  TABLE 9                                                          ______________________________________                                         EMERGENCE AND STEM HEALTH                                                                Emergence (%)   Infection (%)                                        Dust No.  Day 10      Day 38  Stems                                            ______________________________________                                          7        0           0       no stems                                            8 14.3 14.3 100                                                               14 0 0 no stems                                                                15 85.7 100 14                                                                 16 57.1 85.7 0                                                                 17 42.9 85.7 14                                                                18 71.4 100 0                                                                  Untreated 0 0 no stems                                                         Sterile 57.1 100 0                                                           ______________________________________                                    

Example 6

Shepody potato tubers were contaminated/inoculated with Phytophthora infestans and set aside ("source tubers"). After two weeks, one (1) source tuber was cut into quarters through the diseased area with a cutting knife. Without cleaning or changing the knife, five (5) uninoculated Shepody potato tubers were then cut into quarters. This process (1 source tuber/5 uninfected tubers) was repeated to provide enough tubers for 30 replications per treatment (Table 10 below).

The cut tubers (source and uninoculated) were weighed and the appropriate amount of each dust listed in Table 10 below was applied to the tubers by placing the tubers in a double paper bag with dust and then shaking the bag.

The treated tubers were then placed in an unsealed plastic bag (one bag per treatment) and incubated at 10° C., 80-90% RH, for two (2) weeks. After two (2) weeks, the bagged tubers were removed from the 10° C., 80-90% RH environment. The bags were then rolled or shaken to simulate movement from storage to planting areas. The tubers were removed and the spread of P. infestans was determined--% infected tubers. The tubers were warmed to room temperature and planted. The source tubers were not planted. Emergence and infection data were obtained as described above in Example 2 (30 replications/treatment).

The results of this test are listed below in Table 10.

                  TABLE 10                                                         ______________________________________                                         EMERGENCE AND TUBER AND STEM HEALTH                                                                 Infection (%)                                                                  Tubers                                                      Emergence (%) (Before                                                        Dust No.  Day 6   Day 20     planting)                                                                             Stems                                      ______________________________________                                          7        20      86.7       60     40                                            8 26.7 80 40 20                                                               14 20 83.3 20 10                                                               15 30 100 20 0                                                                 17 40 93.3 40 0                                                                18 56.7 100 30 0                                                               19 20 100 30 0                                                                 Untreated 16.7 70 90 40                                                      ______________________________________                                    

Example 7

The procedure described above in Example 6 was repeated using Red Nordland potato tubers. The results of this test are present below in Table 11.

                  TABLE 11                                                         ______________________________________                                         EMERGENCE AND TUBER AND STEM HEALTH                                                                 Infection (%)                                                                  Tubers                                                      Emergence (%) (Before                                                        Dust No.  Day 8   Day 25     planting)                                                                             Stems                                      ______________________________________                                          7        20      83.3       47.5   33                                            8 20 83.3 52.5 33                                                             14 30 70 52.5 0                                                                15 26.7 90 50 0                                                                17 26.7 96.7 45 0                                                              18 36.7 100 45 0                                                               19 20 96.7 35 0                                                                Untreated 10 20 60 33                                                          Sterile 36.7 100 0 0                                                         ______________________________________                                    

The results in Tables 10 and 11 demonstrate that tubers contaminated with P. infestans spread from a contaminated seed source through the cutting and handling of the tubers prior to treatment and planting, still produced plants that were disease free when the tubers were treated in accordance with the present invention prior to planting. 

What is claimed is:
 1. A fungicidal composition comprising an enhanced fungicidally effective amounts ofa) a 2-alkoxyiminoacetamide compound of the formula: ##STR7## wherein R is methyl or ethyl and R¹ is hydrogen, C₁ -C₄ alkyl or allyl; b) an alkylene bis-dithiocarbamate complex salt compound of the formula: ##STR8## wherein R⁴ and R⁵ are each, independently, hydrogen or C₁ -C₆ alkyl; Q is Zn, Fe, or Cu; and the ratio of x to y is from about 3:1 to about 100:1; and c) a thiophanate compound of the formula: ##STR9## wherein R² and R³ are each, independently, C₁ -C₆ alkyl.
 2. A composition as recited in claim 1 wherein R¹ and R², and R³ are each, independently, C₁ -C₄ alkyl, and R⁴ and R⁵ are each, independently, hydrogen or C₁ -C₄ alkyl.
 3. A composition as recited in claim 2 wherein R¹, R², and R³ are each, independently, methyl or ethyl, and R⁴ and R⁵ are each, independently, hydrogen, methyl or ethyl.
 4. A composition as recited in claim 3 wherein Q is Zn and the ratio of x to y is from about 5:1 to about 20:1.
 5. A composition as recited in claim 4 wherein the ratio of x to y is from about 6:1 to about 10:1.
 6. A composition as recited in claim 5 wherein the 2-alkoxyiminoacetamide compound is cymoxanil; the alkylene bis-dithiocarbamate complex salt compound is mancozeb; and the thiophanate compound is thiophanate-methyl.
 7. A composition of claim 1 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 3:1:1 to about 1:16:6.
 8. A composition of claim 1 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 1.5:1:1 to about 1:8:3.
 9. A composition of claim 1 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of about 2.1:10:3.2.
 10. A composition of claim 5 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 3:1:1 to about 1:16:6.
 11. A composition of claim 5 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 1.5:1:1 to about 1:8:3.
 12. A composition of claim 3 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 3:1:1 to about 1:16:6.
 13. A composition of claim 3 wherein said 2-alkoxyiminoacetamide compound, said alkylene bis-dithiocarbamate complex salt compound and said thiophanate compound are present in a ratio of from about 1.5:1:1 to about 1:8:3.
 14. A composition of claim 6 wherein said cymoxanil, said mancozeb, and said thiophanate-methyl are present in a ratio of from about 3:1:1 to about 1:16:6.
 15. A composition of claim 6 wherein said cymoxanil, said mancozeb, and said thiophanate-methyl are present in a ratio of from about 1.5:1:1 to about 1:8:3. 